Analgesic hydrogel microneedle composition for oral mucosa

Abstract

The ketorolac tromethamine (KT) buccal mucosa microneedle KT-BMN system suitable for the complex oral environment is designed and prepared on the basis of the physiological characteristics that buccal mucosa tissue is rich in blood flow, the barrier thickness is small, and the liver first-pass effect does not exist. The KT-BMN adopts polyvinyl alcohol / sodium carboxymethyl cellulose as an adhesive layer and ethyl cellulose as a waterproof layer to form a microneedle system with a double-layer backing structure, so that the retention capacity of the microneedle system in a wet oral environment is enhanced, and the analgesic effect is quickly and effectively exerted.

Description

Technical Field

[0001] This invention relates to the field of medicine. More specifically, this invention relates to a method for preparing a hydrogel microneedle for oral buccal mucosa loaded with analgesics. Background Technology

[0002] Microneedles are needle-like arrays with lengths between 50 and 900 micrometers that deliver drugs transdermally by penetrating the skin / mucous membrane. During the puncture process, microneedles only puncture the surface layer without damaging nerves, allowing drugs to be rapidly absorbed into the body and exert their effects. They offer the advantages of being fast, convenient, and minimally invasive.

[0003] Ketorolac tromethamine (KT) is a novel nonsteroidal anti-inflammatory drug (NSAID) with rapid onset and long duration of analgesia. Its potency is similar to morphine and meperidine, but it is not addictive. Currently available formulations are tablets and injections. Tablets have a slow onset of action and low bioavailability, while injections require specialized personnel for administration and are inconvenient. Microneedle delivery allows direct penetration through the stratum corneum, resulting in rapid onset of action, immediate discontinuation, and good patient compliance. It is particularly suitable for elderly people and children who are uncooperative with injections or oral medications. Summary of the Invention

[0004] One objective of this invention is to provide a novel backing layer for the preparation of oral mucosal hydrogel microneedles, which has the advantages of controllable mechanical strength and strong penetration, making it more suitable as a backing layer for buccal mucosal hydrogel microneedles.

[0005] Another objective of this invention is to provide a method for preparing KT-loaded buccal mucosal microneedles, which can form hydrogel microneedles with good mechanical properties and strong penetrability, exhibiting rapid onset of action, long-lasting efficacy, and quickly exerting the analgesic effect of KT. Figure 1 ).

[0006] To achieve the above objectives, the present invention provides a method for preparing KT buccal microneedles with a double backing layer, specifically comprising:

[0007] 1) Preparation method of KT-BMN backing layer: Dissolve 1.35g of polyvinyl alcohol (PVA) 1788, 0.15g of carboxymethyl cellulose sodium (CMC-Na), and 0.25g of glycerol in 20mL of deionized water, stir and mix evenly, and let stand to remove air bubbles as the adhesive layer solution. Dissolve 1g of ethyl cellulose (EC) in 10mL of anhydrous ethanol as the waterproof layer solution. Coat the adhesive layer solution evenly onto a clean glass plate and dry it in a ventilated environment at 25℃ for 6h. Then, continue to coat the adhesive layer surface with the waterproof layer solution, maintaining a coating height of 50μm, and dry it a second time under the same conditions. After cutting the composite film to the target size, characterize its cross-sectional structure by SEM (5kV): After the sample is frozen in liquid nitrogen for 30s and then fractured, it is fixed on the sample stage, sputter-coated with gold for 60s, and then purged with nitrogen to obtain the final product.

[0008] 2) Preparation of KT-BMN: A solution containing 0.25% LAP and 3% HAMA was prepared, and KT was added to the solution and mixed thoroughly to obtain a buccal mucosa microneedle tip matrix solution containing 0.3 mg / mL KT. 200 μL of the above solution was added in portions to a PDMS buccal mucosa microneedle mold, and the mold was placed in a vacuum environment at 37°C for 20 min to allow the tip solution to fill the mold tip. A suitable waterproof backing layer was cut and applied to the mold surface, and after drying, a complete microneedle patch structure was formed. The PDMS mold was placed at room temperature in the dark for 24 h to dry; finally, KT-BMN was separated from the mold and cured under 405 nm light for 2 min to obtain the final product.

[0009] This invention can form hydrogel microneedles with good mechanical properties, strong penetration, and a double-layer backing structure for use on the oral mucosa. It can enhance the retention capacity in the moist oral environment and help to exert a sustained analgesic effect.

[0010] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0011] Figure 1 Schematic diagram of KT-BMN preparation process

[0012] Figure 2 Scanning electron microscope image of the KT-BMN backing layer

[0013] Figure 3 Scanning electron microscope image of KT-BMN

[0014] Figure 4COMSOL mechanical simulation of KT-BMN

[0015] Figure 5 Force-displacement curves of KT-BMN with different photocuring times

[0016] Figure 6 HE section of rat buccal mucosa tissue after KT-BMN treatment

[0017] Figure 7 (a) Differential scanning calorimetry curve of KT in buccal microneedle matrix of KT-BMN;

[0018] (b) X-ray diffraction pattern

[0019] Figure 8 In vitro cumulative release curve of KT in KT-BMN

[0020] Figure 9 Effects of KT-BMN on carrageenan-induced mechanodynia

[0021] Figure 10 Blood drug concentration-time curves of KT-BMN in rats after intravenous injection of KT and microneedle buccal mucosal administration

[0022] Appendix Explanation

[0023] Table 1. Effects of KT-BMN on formalin-induced pain in rats.

[0024] Table 2 Comparison of pharmacokinetic parameters of KT intravenous injection and microneedle buccal mucosal administration in rats in KT-BMN. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0026] <Example 1> Preparation of KT-BMN backing layer

[0027] Dissolve 1.35g PVA 1788, 0.15g CMC-Na, and 0.25g glycerol in 20mL of deionized water, stir until well mixed, and allow to stand to remove air bubbles to obtain the adhesive layer solution. Dissolve 1g EC in 10mL of anhydrous ethanol to obtain the waterproof layer solution. Apply the adhesive layer solution evenly to a clean glass plate and dry it in a ventilated environment at 25℃ for 6 hours. Then, apply the waterproof layer solution to the adhesive layer surface, maintaining a coating height of 50μm. Dry the plate a second time under the same conditions to obtain the final product.

[0028] Example 1: Characterization of the KT-BMN backing layer

[0029] After the composite film was cut to the target size, its cross-sectional structure was characterized using a scanning electron microscope (5kV): the sample was frozen in liquid nitrogen for 30s to fracture, then fixed on the sample stage, sputtered with gold for 60s, and purged with nitrogen before observation. Figure 2 ).

[0030] <Example 2> Preparation of KT-BMN

[0031] A solution containing 0.25% LAP and 3% HAMA was prepared, and KT was added to the solution and thoroughly mixed to prepare a buccal mucosa microneedle tip matrix solution containing 0.3 mg / mL KT. 200 μL of the above solution was added in portions to a buccal mucosa microneedle PDMS mold, and the mold was placed in a vacuum environment at 37°C for 20 min to allow the tip solution to fill the tip. A suitable waterproof backing layer was cut and applied to the mold surface, and after drying, a complete microneedle patch structure was formed. The PDMS mold was then placed at room temperature in the dark for 24 h to dry. Finally, KT-BMN was separated from the mold and cured under 405 nm light for 2 min to obtain the final product.

[0032] Experimental Example 1: Characterization of KT-BMN Array Morphology

[0033] SEM observations revealed that the KT-BMN needles exhibited good tip morphology, were neatly arranged, and showed no bending or breakage. The needle body was clearly conical, approximately 600 μm in length, with a needle base diameter of approximately 200 μm and a spacing of approximately 500 μm between adjacent needle tips. These parameters are essentially the same as those of the microneedle mold. Figure 3 ).

[0034] Experimental Example 2: Simulation and Measurement of Mechanical Properties of KT-BMN Array

[0035] Mechanical simulations using COMSOL showed that the KT-BMN exhibited minimal deformation after applying a 50 mN axial force, indicating good mechanical strength under stress and ensuring successful microneedle insertion into the buccal mucosa. Figure 4 ).

[0036] Experiment 3: Penetration Performance Study of KT-BMN

[0037] The mechanical properties of KT-BMN were evaluated using a universal pressure testing instrument. As shown in the force-displacement curve, when KT-BMN was subjected to an initial pressure of 50 mN, it gradually deformed, with the curve slope increasing continuously without interruption or sudden drop, indicating that KT-BMN remained structurally stable under stress and did not fracture. Further comparison of the mechanical strength of KT-BMN prepared with different photocuring times revealed that the microneedles cured for 2 minutes exhibited the best mechanical properties. Under 2-minute photocuring conditions, KT-BMN could withstand a pressure of 0.08 N / needle at the maximum displacement, exceeding the minimum force threshold required for buccal mucosal puncture (0.03 N / needle), indicating that the prepared KT-BMN possessed good mechanical strength, enabling successful insertion into the buccal mucosa and providing effective support for drug delivery. Figure 5 ).

[0038] In the field of oral drug delivery, the performance of buccal microneedles inserted into the buccal mucosa is a key factor affecting drug delivery efficiency and therapeutic efficacy. HE analysis shows that the insertion depth of KT-BMN into the buccal mucosa is approximately 120 μm, which accounts for 20% of the total needle length. This indicates that KT-BMN has the ability to penetrate the buccal mucosa, directly delivering drugs to the mucosal tissue beyond the physiological barrier of the mucosal epithelium. Figure 6 ).

[0039] Experiment Example 4: Drug Presence State in Microneedles

[0040] DSC analysis was used to preliminarily determine the state of the drug within the carrier. KT exhibited a significant melting absorption peak at 175.0℃, indicating it is a crystalline substance. No significant absorption peak was observed in the PVA 1788 curve, while HAMA showed a broad but shallow thermal response signal. The physical mixture showed a slightly left-shifted melting peak at 173.69℃, indicating a certain interaction between KT and the matrix material, which may lead to minor perturbations in the crystal structure. No characteristic melting peak of KT was detected in KT-BMN, suggesting that KT does not exist in crystalline form in the microneedle system, but may be dispersed in the polymer network in a molecular or amorphous high-energy state, reflecting good compatibility and drug loading morphology transformation. Figure 7 a). XRD, as an effective means of detecting sample crystallization behavior, further verified the above conclusion. XRD pattern ( Figure 7(b) shows that the KT raw material exhibits multiple sharp diffraction peaks within the corresponding diffraction angle range, further confirming its crystalline properties. Characteristic diffraction peaks of KT and PVA 1788 are still identifiable in the physical mixture, indicating that the crystal structure of both was not completely destroyed in the physical mixing state. However, in the diffraction pattern of KT-BMN, the characteristic diffraction peaks of KT essentially disappear, the overall diffraction intensity is significantly reduced, and the spectrum exhibits typical diffuse scattering characteristics, indicating that the number of crystals in the microneedle system is reduced, and the amorphous component dominates. This result is supported by DSC analysis, jointly proving that KT exists in an amorphous solid dispersion form within the microneedles, which is beneficial for improving drug solubility and release performance. In summary, the DSC and XRD results consistently show that KT successfully transforms from a crystalline to an amorphous state in KT-BMN. This phase transformation helps enhance drug solubility and provides an important basis for microneedle drug delivery. Figure 7 ).

[0041] Experimental Example 5: Drug Release Curve in Microneedles

[0042] The in vitro drug release behavior of KT-BMN was studied using a transdermal diffusion cell. Experimental results showed that KT-BMN exhibited extremely rapid and significant drug release. Within 5 minutes of administration, the drug was rapidly released, with a cumulative release rate as high as 5%. This rapid initial burst release effect indicates that KT-BMN can immediately establish an efficient drug diffusion channel after insertion into the simulated mucosa. The release process reached a peak within 1 hour, with a cumulative release rate of 38%, reaching 55.33% by 2 hours. Subsequently, the release rate gradually slowed down, leveling off after 6-8 hours, and stabilizing at a plateau of 76.77% at 12 hours. The release curve clearly exhibited a typical biphasic characteristic: an initial rapid release phase followed by a sustained release phase. The initial burst release facilitates the rapid achievement of effective therapeutic concentrations at the application site, which is of great significance for relieving acute symptoms such as oral ulcers, while the subsequent sustained release helps maintain the therapeutic effect for a longer period. The entire release process was essentially completed within 12 hours, indicating that KT-BMN can achieve efficient drug delivery and high bioavailability. KT-BMN exhibited excellent rapid drug release performance and high cumulative release in a simulated oral mucosal environment, providing solid experimental evidence for its development into a highly efficient oral mucosal drug delivery system. Figure 8 ).

[0043] <Example 3> Evaluation of the analgesic effect of ketoroxyprogesterone tromethamine buccal microneedles KT-BMN

[0044] Evaluation of KT-BMN's inhibitory effect on formalin-induced phase II pain: Twenty-four male SD rats were randomly divided into four groups (n=6). Before the experiment, all rats were sedated by isoflurane inhalation anesthesia. After the anesthesia stabilized, the following groupings were performed: the model group received 0.2 mL of physiological saline intravenously; the KT injection group received 0.2 mL of KT solution at a concentration of 7 mg / mL intravenously; the blank buccal mucosa microneedle group had a blank buccal mucosa microneedle applied to the rat's buccal mucosa and pressed for 1 min to ensure microneedle penetration; the KT-BMN group had a KT-BMN microneedle applied, pressed, and fixed in the same manner. Sixty min after administration, 100 μL of 5% formalin solution was subcutaneously injected into the right hind paw of each group of rats, with the formation of a wheal indicating successful injection. Immediately after injection, observe and record the rats' licking and biting behavior on their right hind paw: Phase I pain response time was the total time rats licked and bit their paw within 0-10 min after formalin injection; Phase II pain response time was the total time rats licked and bit their paw within 10-60 min after injection (Table 1).

[0045] Analgesic evaluation of KT-BMN in a carrageenan-induced pain model: Forty male SD rats were randomly divided into 5 groups (n=8). Before the experiment, all rats were sedated by isoflurane inhalation anesthesia. After stabilization, the following groupings were performed: the control group and model group received an intravenous injection of equal volumes of physiological saline; the KT injection group received an intravenous injection of 0.2 mL of KT solution at a concentration of 7 mg / mL; the blank buccal mucosa microneedle group had a blank buccal mucosa microneedle applied to the rat's buccal mucosa, pressed for 1 min to allow the microneedle to penetrate and fix it; the KT-BMN group had a piece of KT-BMN applied, pressed, and fixed in the same manner. Except for the control group, all other groups received a subcutaneous injection of 100 μL of 1% carrageenan solution into the left hind paw to establish an inflammatory pain model. Appropriate drug treatments were administered 30 min after injection, and the mechanical pain threshold was measured every 30 min. During the measurement, Von Frey fibers were used to stimulate the sole of the rat's hind paw, and the stimulation intensity was gradually increased. The minimum stimulation intensity at which the rat exhibited a paw withdrawal response was recorded as the mechanical pain threshold. Figure 9 ).

[0046] <Example 4> Pharmacokinetic Study of KT Intravenous Injection and KT-BMN Administration in Rats

[0047] Twelve SD rats were randomly divided into a KT intravenous injection group and a KT-BMN group (n=6). The KT intravenous injection group received a dose of 10 mg / kg, while the KT-BMN group received one microneedle of the same dosage. Blood samples were collected from the orbital sinus of both groups at 5 min, 30 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h, and 48 h after drug administration. The blood samples were collected in heparin sodium anticoagulant tubes and centrifuged at 4000 rpm for 10 min at 4°C. The supernatant was collected for later use. 5 μL of rat blank plasma was precisely pipetted into a 1.5 mL centrifuge tube, and 10.0 μL of 155 acetonitrile solution (100 ng / mL) was added. The mixture was vortexed, and then 135 μL of acetonitrile was added again. The mixture was vortexed for 10 min, centrifuged at 3900 rpm for 10 min, and 60 μL of the supernatant was aspirated and 60 μL of deionized water was added. The mixture was vortexed for 5 min and then injected into a sample tube for analysis. All plasma samples were processed and analyzed according to the above plasma sample pretreatment steps. Pharmacokinetic parameters, including Cp, were calculated using DAS2.0 software after intravenous injection and buccal mucosal administration in rats. max t max AUC 0-∞ MRT 0-∞ wait( Figure 10 (Table 2).

[0048] Table 1. Effects of KT-BMN on formalin-induced pain in rats.

[0049]

[0050] Table 2 Comparison of pharmacokinetic parameters of KT intravenous injection and microneedle buccal mucosal administration in rats in KT-BMN.

[0051]

Claims

1. The preparation of the KT-BMN backing layer, characterized in that: A microneedle system with a double-layer backing structure is formed by using polyvinyl alcohol / sodium carboxymethyl cellulose as the adhesive layer and ethyl cellulose as the waterproof layer, which enhances the retention ability of microneedles in the moist oral environment.

2. A method for preparing KT-BMN, characterized in that: 1) Prepare a solution containing 0.25% phenyl (2,4,6-trimethylbenzoyl) lithium phosphate (LAP) and 3% methacryloyl hyaluronic acid (HAMA), and add KT to the solution and mix thoroughly to prepare a mucosal microneedle tip matrix solution containing 0.3 mg / mL KT. 2) Take 200 μL of the above solution and add it in portions to the buccal mucosa microneedle polydimethylsiloxane mold. Place the mold in a vacuum environment at 37°C for 20 minutes to allow the solution to fill the tip of the mold. Cut a suitable waterproof backing layer to cover the surface of the mold and dry them together to form a complete microneedle patch. 3) Place the polydimethylsiloxane mold at room temperature in the dark for 24 hours to allow it to dry. Finally, separate the obtained KT-BMN from the mold and cure it under 405nm light for 2 minutes to obtain the final product.

3. The preparation method of KT-BMN as described in claim 2, characterized in that... The microneedle tip is a conical array mold.

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